Rope-drive elevator.



. 1'. H. VENN.

ROPE DRIVE ELEVATOR. 'Arrpmumi rum) JUL! 6, 1001.

Patented July 19,1910

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I. H. VENN. ROPE DRIVE ELEVATOR.

APPLIOETION FILED JULY 6,1907.

964,889. Patented July 19,1910.

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LILVENN. ROPE DRIVE ELEVATOR. I APPLIOATION I'ILEDJ'ULY 6,1907.

Patented July 19,1910.

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INVENTOR ATTORNEY THE NORRIS PETERS cm, WASHINGTON, a c. I

UNITED STATES PATENT OFFICE.

ISAAC H. VENN, OF YONKERS, NEW YORK, ASSIGNOR TO OTIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ROPE-DRIVE ELEVATOR.

To all whom it may concern:

Be it known that I, ISAAC H. VENN, a citi- Zen of the United States, residing in Yonkers, in the county of Westchester and State of New York, have invented a new and useful Improvement in Rope-Drive Elevators, of which the following is a specification.

My invention relates to rope drives for traction elevators, and has for its object the provision of means for preventing slipping between the hoisting cable and the drive sheave or pulley, when the load on the elevator car is increased.

In the forms of traction elevators in common use, the elevator car is operated by a cable secured at one end to the car, passing about the drive sheave of the motor and having a counterweight secured to its other end. The counterweight is usually made heavy enough to balance the car with its average load, so that with the motor at rest there is no tendency of the cable to slip. hen the load on the car is increased the counterweight will be overbalanced and the cable will tend to slip about the drive sheave. If the load becomes great enough the frictional resistance between the cable and drive sheave is overcome and the cable will slip, so that the motor is unable to hold the car stationary. Also, when the car is thus overloaded the motor is unable to lift it, as the drive sheave will slip on the cable. It is found in practice that the tension on the cable leading from the load to the drive sheave can only be about 50 per cent. more than that leading from the counterweight to the sheave. If this ratio is exceeded, slipping will occur. In order to overcome this objection I have devised means for increasing the tension of the cable on both sides of the driving sheave as the load on the car increases, so that the load may be greatly increased without causing the cable to slip.

In the accompanying drawings which embody several forms of my invention, Figure 1 is a view of a traction elevator system and shows an arrangement of parts whereby the tension on the counterweight cable is increased as the load on the car increases; Figs. 2, 3 and 4c are similar views showing various modifications.

Like reference characters are used to designate corresponding parts throughout the several views.

Referring particularly to Fig. 1, C denotes Specification of Letters Patent.

Application filed July 6, 1907.

Patented July 19, 1910.

Serial' No. 382,485.

an elevator car of common form operated by power from the motor shaft M through the drive sheave or pulley D and hoisting cable H. A combined reversing switch and rheostat A for the motor is controlled by the switch B in the elevator car. The abovenamed parts are old and well known in the art and need no further description.

The hoisting cable H is connected at one end to a frame F which carries a counterweight VV. The cable extends from the frame F upwardly and over a sheave 1, down to the sheave 2 journaled in the frame F, up to and over the sheave 3, down and around the drive sheave D, up over the sheave 5, downwardly on the right hand side of sheave 5, again under the drive sheave D, upwardly and over the sheave 6, downwardly and under the sheave 7 journaled in bearings on the upper side of the car O, upwardly over the sheave 8, across to and over the sheave 9, downwardly to and around the sheave l0, and upwardly to the frame F where the other end of the cable is secured. The sheaves 1, 8, 6, 8 and 9 are journaled in bearings secured to the overhead beams I at the top of the elevator shaft. The sheave 10 is journaled in bearings secured to the floor at the bottom of the elevator shaft. The sheave 5 journaled in an extension of the motor frame is for the purpose of increas ing the area of contact between the cable H and the drive sheave D, as with this arrangement the cable has two sections in engagement with the drive sheave, thus increasing the frictional resistance.

It will be observed that the weight of the car C with its load is sustained by the two leads 11 and 12 of the hoisting cable, the sheave 7 permitting an equal division of 95 the weight. The weight of the counterweight WV is equally divided between the three leads 13, 14k and 15, each of these leads supporting onethird of the weight W.

In explaining the operation of the device 100 let it be assumed for the time being that the frictional resistance of the sheaves in their bearings, and the weight of the cable are neglected, the weight of the moving parts being considered as divided between the car 105 C and counterweight W. To understand clearly the invention, it must be remembered that all the sheaves except the drive sheave D are journaled for free rotation and act simply as direction sheaves without changing the tension on the various leads of the cable. Thus the portion of the cable extending from the left hand side of the drive sheave D to the counterweight W is all under the same tension. That is, the tension on each of the leads 19, 12, 11, 18, 17 and 16 is the same: Likewise the tension on the cable between the right hand side of the drive sheave D and the frame F is the same throughout, the tension onthe leads 20, 13, 15 and .1 1 being equal. The difference between the tensions on the leads 19 and 20 represents the force tending to produce slipping between the drive sheave D and the cable. It also represents the frictional resistance that must be applied at the periphery of the drive sheave to hold the elevator car suspended, this resistance being a power, which power must be exceeded to effect the lifting of the car. The weight of the car C with its load being equally divided between the leads 11 and 12, the tension on the lead 12, and therefore the tension on the lead 19 extending from the left hand side of the drive sheave D, is one-half the weight of the car and its load. This tension is transmitted through the leads 11, 18, 17 and 16 to the counterweight W, exerting a downward pull onsaid counterweight equal to one-half the weight of the car and its load, so that the total weight or downward pull on the frame F is the weight of the counterweight W plus one-half the weight of the car and its load. This weight being equally divided between the three leads 13, 1st, 15, the tension onthe lead 20 will be one-third thisweight. That is, the tension on-the lead 20 will be equal to one-thirdthe counterweight plus one-sixth of the weight of the car and its load. Letting L represent the weight of the car and its load and \V the counterweight, we have the tension on lead 20 as g, V L. Also the tension on the lead 19, is e L. Now any increase in the load L will not only increase the tension on the lead 19, but will also increase the tension on the lead 20, so that the load may be increased to, a greater extent before slipping of the cable will occur than would be the case with the ordinary arrangement. Foi example, an average load L of 1,800. lbs. will be balanced by a counterweight W' of 1,800 lbs. That is, the tension on the lead 19 is L or 900 lbs, and the tension on the lead 20 is 3 V L or 600 lbs. 300 lbs. 900 lbs. There is therefore an equal tension on the leads, 19 and 20. If now, the load L is increased, for example to 3,000 lbs,, the tension on the lead 19 is 1,500 lbs, and the tension on the lead 20 W L) is 600 500 1,100 lbs. The tension on the lead 19 is therefore onlytOO lbs. more than that on the lead 20. 'This is considerably less than 50 per cent. of 1,100 lbs., which as before pointed out is the amount the load on the lead 19 may be increased over that on the lead 20 before slipping will occur. Comparing this with the usual arrangement of car, counterweight and cable in which a load Lof 1,800 lbs. is balanced by a counterweight of 1,800 lbs, it will be seen that if the load L is increased to 3,000 lbs, the tension on the cable leading from the drive sheave to the load is 3,000 lbs. and that on the cable leading to the drive sheave remains 1,800 lbs. But 1,800 lbs. onone side of the drive will only sustain 2,700 lbs. on the opposite side. The load is therefore 300 lbs. in excess of what may be carried before slipping will occur.

The above comparison is given to show that with my device the load may be safely increased to a point far beyond what may be carried with the usual arrangement. It may be readily shown that with my device the normal load including the weight of the car may be increased 100% before the slipping point occurs. As an example, a load L of 1,800 lbs. is balanced by a counterweight of 1,800 lbs. 7 If we double the load L, making it 3,600 lbs, the tension on the lead 19 L) is 1,800 lbs. The tension on the lead 20 (a, W+% L) (s00+c00:1,200 lbs. That is, thetension on the lead 19 is 50% more than that on the lead 20 when the load L is increased 100%. It is also apparent that with my arrangement, when the load L is decreased so that it is over-balanced by the counterweight W, the tension on the lead 20 is reduced as well as that .on the lead 19, which results in a smaller difierence between the tensions on leads 19 and 20, so that the load L may be reduced to a greater extent than would otherwise be the case, before slipping would occur.

The operation of my invention may be explained in another way, follows :-A given counterweight V will exert a certain tension on the lead 20, which does not vary with the load. The load L transmits a tension to the lead 19 which is proportional to the load. In these respects the operation is the same as with the usual arrangement. But in addition to this a certain proportion of the load is transmitted to the lead 20 and as this varies with the load, an increase of load increases the tension on the lead 20 as well as the lead 19, and a decrease in the load decreases the tension on both leads 19 and 20. The difference in the tensions on leads 19 and 20 is therefore less for any variations of the load from the normal, than with the usual arrangement.

In the above explanation and examples it has been assumed that the leads 13, 1 1, 15, are vertical and in line with the lead 10. But this is only for the purpose of illustration, as the ropes may be arranged as desired. The moments of forces in the directions of the leads 13 and 15 which are inclined to the vertical are the resultants of ios horizontal and vertical components. As the vertical components represent the vertical tension of the lead 16, the resultants in the direction of the leads 13 and 15 are greater than the vertical force. That is, the tension on the leads 13 and 15 is greater than if they were vertical. As a result, the tension on the lead 20 is more than one-third the downward pull 011 the frame F. This effect is only slight when the car is near its upper limit of travel, but when the car is at its lower limit of travel, and the counterweight near the sheaves 1 and 3, the effect is greatly increased. As a practical result the tension on the cable 20 is greatest when the car is at the bottom of its travel and apt to be heavily loaded, and decreases as the elevator rises and part of the load is removed.

Referring now to Fig. 2, a somewhat different arrangement of sheaves and cables is shown, but the same results are obtained. In this arrangement two sets of cables H and H are used. The cables H are connected to the car C and pass over a sheave 21, and have a lead 22 extending downwardly and connected to the frame of the sheave 6. The cables H extend downwardly from the frame F, and then beneath the sheaves l0, 9 up, and over the sheave 6 and downwardly to the drive sheave D. The arrangement of the remainder of these cables and their direction sheaves is the same as in Fig. 1. The weight of the load is transmitted through the cables H and equally divided between the leads 19 and 23 of the cables H. The tension on the lead 19 is therefore one-half of the load or L. The tension on the lead 23 which is L is transmitted to the counterweight WV and substantially one-third of this is transmitted through lead 13 to lead 20. The tension on lead 20 is therefore gg- L-H; W. It will thus be seen that the tensions on the leads 19 and 20 are the same as in Fig. 1 for corresponding loads.

Fig. 3 shows a further modification in which somewhat different results are attained. In this form two sets of cables H 1 1 are used. The cables H are secured at one end to the overhead beam I at the point 2%, extend down around the sheave 2, up and over the sheave 25, down and around the sheave 2 again, and from the sheave 2 to the sheaves 26, D, 5, D, 6, 27, 28, 29, and are secured at the fixed point 30. The frame F carrying the counterweight IV is in this case supported by four leads 31, 32, 33, 34, so that only one-fourth the tension is transmitted to the lead 20. The tension on the leads 19 and 35 is due to the load L acting through the cables H and sheave G. The tension 011 each lead is more than onehalf the load L, as the leads 19 and 35 extend at an angle to the cables H This tension is transmitted to the leads 36 and 37 extending to the sheave 29. The resultant downward pull on the sheave 29 is somewhat less than the tensions on the lead 36 plus the tension on lead 37, owing to the inclined directions of the leads. If the leads 36 and 37 are equally inclined with the leads 35 and 19, respectively, the downward pull on the sheave 29 is equal to the load L. One-fourth of this pull is transmitted to the lead 20. The total tension on the lead 20 is therefore i-VV+-l-L, and the tension on the lead 19 is somewhat more than %L. The effect of increasing the load is therefore to increase the tension on both leads l9 and 20, and of decreasing the load to decrease the tension on both leads, the principle of operation being substantially the same as in Figs. 1 and 2. In this case also the load L may be increased to double the amount needed to keep the parts balanced, before the tension on the lead 19 is 50% more than that on the lead 20.

Fig. 4 shows still another modification. The arrangement is substantially like that shown in Fig. 1, except that the frame F instead of being supported by three leads as in Fig. 1, is supported by two leads 13 and 5L1, the end of the cable being secured to the fixed overhead frame I. One-half the downward pull on the frame F is therefore transmitted to the lead 20. The tension then, on the lead 20 is {W-t-iL, and the tension on the lead 19 is gL. The weight IV must be one-half the load L to balance the parts, and make the tension on the leads 19 and 20 equal. This will appear from the equation %L:! /V+%L. Solving, we find the load 21V. To find the load that will be necessary to increase the tension on the lead 19 to 50% more than that on the lead 20, the following equation may be made, {-L: 1,} (gWV-l-iL). Solving, we get L:6W. That is, the load L may be increased to three times what it is when the parts are balanced, before the tension on the lead 19 is 50% in excess of that on the lead 20.

Of course what is true in regard to the addition or subtraction of actual load is also true in regard to overcoming inertia in starting and stopping the car. I

It should be particularly noted that Figs. 1, 2 and 3 illustrate 1: 1 arrangements as to the relative movement of the car and counterweight. If the counterweight is lifted three feet in Fig. 1, for example, any given point on the lead 13, 20 or 19 moves nine feet. This tends to let the car descend 4!; feet, but it should be observed that when the counterweight is lifted 3 feet the leads 17, 18 and 11 move also 3 feet. This tends to lift the car 1%; feet. The difference li-1:}:3 feet represents the actual descent of the car. In the same manner it may be shown that the car and counterweight in Fig. 2 move over substantially equal distances in the operation of the elevator.

In Fig; 3 when the counterweight WV niovesiipwar'dly 1 foot, the leads and 19 move four feet and this tends to let the car descend 2 feet. The upward movement of the counterweight, however, will move the leads 36 and two feet and this tends to lift the car onefoot. The resultant action is a descent of the car 1 foot which is equal to the rise Of the counterweight:

In F ig; 4: if the coiinterweight IV ase'ends 1 foot the leads 20 and 19 move 2 feet and the ear tends to descend 1 foot. The upward movement of the counterweight 1 foot tends to move the car upwardly foot, so that the car d'seends only foot while the connt'er'weight ascends twice that distame. This then is a %:1 arrangement. Other ratios may be obtained if desired, but in most instances it may be preferred to have the car and counterweight move over equal distances. More tension, however, is transmitted from the car to the counterweight in the arrangement of Fig. 1.

Althoi1g'h I have shown my invention applied to an elevator to which it is particularly adapted, it should be understood that it may have a general application. Furthermore; it is obvious that various changes in the details and arrangement of parts may be made by those skilled in the art without departing from the spirit and scope of my invention as defined by the claims and I desire therefore not to be limited to the precise construction herein disclosed;

What I claim as new and desire to have protected by Letters Patent of the United States is 1. The combination with a driving element, of a flexible member in frictional engagement therewith, a load connected to one lead of said flexible member and holding the same under tension on one side of the driving eleinent, a device effecting a constant tension on the opposite lead, and a connection between the load and the said tensioning-d'evice to vary the tension in the opposite lead as the load varies.

2. The combination with a driving ele ment, of a flexible member in contact therewith, means for placing a variable tension on the flexible member on one side of said element, and means for holding the flexible member on the opposite side of the said element with a variable tension equal to the sum of a constant tension, and a tension proportional to the tension on the first side of said element.

3. The combination with a driving element, of a flexible member in driving contact therewith, a load connected to the flexible member and exerting a pull thereon on one side of the said driving element proportional to the load, means for exerting a constant pull on the flexible member on the opposite side of the driving element, and a connection to effect an additional pull on said last-named side varying with the load.

4. The combination with a driving element, of a flexible member in driving connection therewith, a load connected to the flexible member and exerting a pull thereon on one side of the driving element proportional to the load, means for exerting a constant pull on the flexible member on the opposit'e side of the said element, and means to effect an additional pull on said lastnamed side proportional to the pull 011 the first-named side.

5. The combination with a driving element, of a flexible member in engagement therewith, a load connected to the flexible member and holding it under tension on one side of the driving element, means for exerting a constant tension on the flexible member on the opposite side of the driving element, and means for sustaining a portion of the load on the flexible member on the first side of the driving element, and adding it to the said constant tension.

, 6. The combination with a sheave, of means for driving thesame, a cable in driving contact with said sheave, a movable body exerting tension on the lead of said cable extending from one side of said sheave, a tensioning device for the opposite lead, and a connection between said movable body and said tensioning-devi'ce to add tension to the opposite lead in accordance with variations of load.

7 The combination with frictional driving apparatus, of a power-transmitting cable associated therewith, said cable having its ends connected together, and a device connected to an intermediate continuous portion of said cable, movable in unison with the cable, and exerting a tension in the latter in both sets of the leads extending from the driving apparatus.

8; The combination with driving means, of a cable in frictional engagement with the said driving means, a device operated by the cable and exerting a tension thereon on one side of the driving means, a weight connected to the cable on the opposite side of the driving means and holding it under tension, and a connection for transmitting tension from said device to said weight to increase the eifect of the latter.

9. In an elevator, the combination with driving apparatus, of a load-carrying device, a flexible member associated with the driving apparatus and operatively connected to the load-carrying device, a tensioning appliance for the portion of the cable on the side of the driving apparatus remote from the load, and a connection between the load-carrying device and the tensioning appliance to increase the effect of the latter in proportion to variations of load.

10; In an elevator, the combination with a motor, of a drive sheave, a cable in en gagement therewith, a load-carrying device connected to the cable, a constant tensioning appliance, and means for transmitting a portion of the tension in the cable due to the load to the said appliance to increase the tension in the cable on the side of the drive sheave remote from the load.

11. In an elevator, the combination with a motor, of a drive sheave therefor, a cable in engagement therewith, a load-carrying device connected to the cable, and exerting a tension thereon on one side of the drive sheave, means for transmitting a portion of the tension due to the load in proportion to the latter to the opposite side of the drive sheave, and means for adding a constant tension thereto.

12. In an elevator, the combination with a motor and a drive sheave, of a cable engaging the sheave and having leads extending from opposite sides of the sheave, a load-carrying device connected to and exerting tension on one lead, means for exerting a constant tension 011 the opposite lead, and a direct connection for adding thereto a tension proportional to the load.

13. In an elevator, the combination with a motor and a drive sheave, of a cable engaging the sheave and having leads extending from the sheave, a load-carrying device connected to and exerting tension on one lead, acounterweight connected to the cable and exerting tension on the other lead, and a direct connection for adding to the tension on said last-named lead a tension proportional to the weight of the load-carrying device and its load.

14. In an elevator, the combination with a motor and a drive sheave, of a cable in engagement with the drive sheave, a loadcarrying device, a tensioning appliance means connecting the load-carrying device with the cable and dividing the weight of the load-carrying device and its load between two portions of the cable, one of said portions extending directly to the drive sheave and the other portion extending to said tensioning appliance, the latter being connected to the lead from the opposite side of the drive sheave.

15. In an elevator, the combination with a motor and a drive sheave, of a load-carrying device, a sheave connected thereto and supporting its' weight, a cable in engagement with said sheaves and transmitting a portion of the weight of the load-carrying device and its load to the drive sheave through one lead of the cable, and means for transmitting another portion of said weight to the drive sheave through another lead of the cable.

16. In an elevator, the combination with a motor and a drive sheave, of direction sheaves, a load-carrying device, a sheave connected thereto, a cable in engagement with each of said sheaves, and supporting the Weight of the load-carrying device and its load, one portion of the cable transmitting one-half of said weight to one side of the motor sheave, and means for transmitting a portion of the other half of the weight to the other side of the motor sheave.

17. In an elevator, the combination with a motor and a drive sheave, of a cable in engagement therewith and having leads extending therefrom, a load-carrying device supported by the cable and transmitting a portion of its weight to one of the leads extending from the drive sheave, means for transmitting a portion of the remainder of said weight to the other lead, and a counterweight connected to the cable and having a portion of its weight transmitted to the lastnamed lead.

18. In an elevator, the combination with frictional driving apparatus comprising a sheave, of a car, a sheave connected to the car, additional sheaves journaled in fixed supports at the upper end of the elevator well, a counterweight, a frame carrying said counterweight, a sheave journaled in said frame, a sheave journaled in a fixed support at or near the lower end of the elevator well, and cables connected with all of said sheaves to permit the car and its load to exert tension in both leads extending from the driving sheave in proportion to the load.

19. In a traction elevator, the combination with frictional driving apparatus, of powertransmitting or driving cables associated therewith, a car and a counterweight, and sheaves associated with said cables to permit the car and its load to transmit tension directly to one lead extending from the driving apparatus and to exert a direct pull on the counterweight to assist the latter in producing tension in the opposite lead.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

ISAAC H. VENN.

Witnesses:

JAMES D. IVERS, CHAS M. NISSEN. 

